Control system for a vehicle

ABSTRACT

A control system is disclosed for use in a zero turn vehicle, including an electric controller in communication with a pair of independent drive units. A joystick provides user inputs to the controller to control the rotational speed and direction of the drive units. The joystick includes a vertical stalk pivotable between a plurality of pivot positions, where each of the plurality of pivot positions corresponds to a particular rotational speed and direction of each of the driven wheels. A selector switch may be used to select one of a plurality of driving modes stored in the electric controller, wherein each of the plurality of driving modes maps a different set of speeds and directions for each of the driven wheels onto the plurality of pivot positions. The joystick may also rotate about a vertical axis to provide zero turn capability.

CROSS REFERENCE

This application is a continuation of U.S. Non-Provisional patentapplication Ser. No. 14/790,675 filed on Jul. 2, 2015, which claims thebenefit of U.S. Provisional Patent App. No. 62/020,612 filed on Jul. 3,2014. The contents of these prior applications are incorporated hereinby reference in their entirety.

BACKGROUND OF THE INVENTION

This disclosure is generally related to drive and directional controldevices for vehicles.

This disclosure is generally related to drive and directional controlsystems for vehicles in general, and more particularly to drive systemsand directional control systems for utility vehicles such as, forexample, lawn and garden tractors and mowers.

Traditional utility vehicle travel control is accomplished by acombination of driven wheels, steered wheels, a steering control, atransmission control, and a throttle. The operator or user of such atraditional vehicle may first select a forward or reverse gear with thetransmission control, then set the throttle to a speed of travel, andthen steer the vehicle. This type of vehicle travel control is normallyassociated with vehicles having a relatively wide turning radius andlimited maneuverability in tight quarters.

In an attempt to improve maneuverability, zero turn vehicles, such aszero turn mowers, were introduced. A zero turn style vehicle typicallyuses independently controlled transaxles or wheel motors to providesteering by selectively speeding up, slowing down, or changing thedirection of rotation of the driven wheels on each side of the vehicle.Typically, a user manipulates a pair of levers to control the speed anddirection of the output of a transaxle on each side of the vehicle. Ifthe user wishes to move the vehicle forward, he presses both leversforward. If the user wishes to move the vehicle backwards, he pulls thelevers back. To steer the vehicle to the left, the right side lever ispushed further than the left, and to execute a very tight turn to theleft, the user can pull the left lever back while pressing the rightlever forward to execute a zero radius, or near zero radius turn.

The steering wheel method is easy to use but may lack maneuverabilityand programming flexibility when compared to a joystick control systemand the lever activated differential steering systems may simply be moredifficult to use for some vehicle operators. This disclosure is directedto addressing the problems and needs of travel control systems in thegeneral area of highly maneuverable utility vehicles.

SUMMARY OF THE INVENTION

The present invention comprises a control system for a utility vehiclecapable of traveling in a variety of different directions and turning ina zero turn manner. The control system incorporates a multi-axis userinterface such as a joystick connected to a controller forproportionally controlling the direction and speed of the vehicle, andfor providing different manners in which the vehicle may enter zero-turnmode. The joystick may include at least one selector switch, such as apushbutton, for switching between programmed travel modes or selectingan auxiliary function.

A better understanding of the invention will be obtained from thefollowing detailed descriptions and accompanying drawings, which setforth illustrative embodiments that are indicative of the various waysin which the principals of the invention may be employed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of a first exemplary vehicle incorporating thecontrol system as disclosed herein.

FIG. 2 is a top plan view of a second exemplary vehicle incorporatingthe control system as disclosed herein.

FIG. 3 is a top plan view of a third exemplary vehicle incorporating thecontrol system as disclosed herein.

FIG. 4 is a top plan view of a fourth exemplary vehicle incorporatingthe control system as disclosed herein.

FIG. 5 is a top plan view of a fifth exemplary vehicle incorporating thecontrol system as disclosed herein.

FIG. 6 is a top plan view of a sixth exemplary vehicle incorporating thecontrol system as disclosed herein.

FIG. 7 is a perspective view of a joystick-style input device inaccordance with the present invention.

FIG. 8 is a representation of certain possible drive positions of thejoystick of the present invention, without any additional programming tocontrol or modulate the vehicle output.

FIG. 9 is a graph of the drive outputs corresponding to the positions ofthe joystick depicted in FIG. 8.

FIG. 10 is a representation of the vehicle movements corresponding tothe positions of the joystick depicted in FIG. 8.

FIG. 11 is a representation of certain possible drive positions of thejoystick of the present invention, using a first set of instructions forcontrolling and modulating the vehicle output.

FIG. 12 is a graph of the drive outputs corresponding to the positionsof the joystick depicted in FIG. 11.

FIG. 13 is a representation of the vehicle movements corresponding tothe positions of the joystick depicted in FIG. 11.

FIG. 14 is a representation of certain possible drive positions of thejoystick of the present invention, using a second set of instructionsfor controlling and modulating the vehicle output.

FIG. 15 is a graph of the drive outputs corresponding to the positionsof the joystick depicted in FIG. 14.

FIG. 16 is a representation of the vehicle movements corresponding tothe positions of the joystick depicted in FIG. 14.

FIG. 17 is a representation of certain possible drive positions of thejoystick of the present invention, using a third set of instructions forcontrolling and modulating the vehicle output.

FIG. 18 is a graph of the drive outputs corresponding to the positionsof the joystick depicted in FIG. 17.

FIG. 19 is a representation of the vehicle movements corresponding tothe positions of the joystick depicted in FIG. 17.

FIG. 20 is a representation of the possible drive positions of thejoystick of the present invention, using the second set of instructionsfor controlling and modulating the vehicle output as depicted in FIG. 14but also incorporating physical stops for the joystick.

DETAILED DESCRIPTION OF THE DRAWINGS

The description that follows describes, illustrates and exemplifies oneor more embodiments of the invention in accordance with its principles.This description is not provided to limit the invention to theembodiments described herein, but rather to explain and teach theprinciples of the invention in order to enable one of ordinary skill inthe art to understand these principles and, with that understanding, beable to apply them to practice not only the embodiments describedherein, but also any other embodiment that may come to mind inaccordance with these principles. The scope of the invention is intendedto cover all such embodiments that may fall within the scope of theappended claims, either literally or under the doctrine of equivalents.

It should be noted that in the description and drawings, like orsubstantially similar elements may be labeled with the same referencenumerals. However, sometimes these elements may be labeled withdiffering numbers or serial numbers in cases where such labelingfacilitates a more clear description. Additionally, the drawings setforth herein are not necessarily drawn to scale, and in some instancesproportions may have been exaggerated to more clearly depict certainfeatures. As stated above, this specification is intended to be taken asa whole and interpreted in accordance with the principles of theinvention as taught herein and understood by one of ordinary skill inthe art.

FIGS. 1, 2, 3, 4, 5 and 6 represent various exemplary vehicles in whichthe control system of the present invention could be used. FIG. 1depicts a hybrid zero turn vehicle, namely rear engine rider 100 havinga prime mover 120, which could be an internal combustion engine,disposed on frame 110. A pair of electric transaxles 130L and 130Rdrives a pair of rear wheels 116L and 116R, and a pair of front casters112 permits zero turn rotation of the vehicle 100. Other standardelements, such as seat 115, deck 117, discharge chute 118 and blades119, are depicted in a representational manner, as the specifics ofthese features are not critical to the present disclosure. Prime mover120 powers a pair of alternators 121 through a standard belt and pulleyor other known drive system 123. Alternators 121 in turn charge thebattery 124 through conductors 125. It will be understood that battery124 may be one of various available types and sizes, and may comprisemore than one battery unit, depending on the desired power requirementsand operating characteristics of the vehicle. Bus 134 connects mastercontroller 132M to slave controller 132S and master controller 132M isconnected to joystick 140 by means of conductor 141. It will beunderstood that joystick 140 could also be wirelessly connected tomaster controller 132M by known technology and that controllers 132M and132S could be combined into a single controller.

The electric transaxles 130L and 130R depicted herein may be similar inconstruction to those depicted in U.S. Pat. No. 8,668,036, the terms ofwhich are incorporated herein by reference. It will be understood thatthose elements of the vehicle which are important to the ability of theuser to turn the vehicle, such as the electric transaxles 130L and 130R,are designated using left and right designations, simply for ease ofdescription. Other elements which may have more than one component suchas the alternators 121, but for whom location is not critical, do notuse left and right designations.

Additional types of utility vehicles 200, 300, 400, 500 and 600 aredepicted in FIGS. 2, 3, 4, 5 and 6, respectively, and are describedbelow. Many aspects of these vehicles 200, 300, 400, 500 and 600 aresimilar to those in vehicle 100, such as frame 210, 310, 410, 510, 610,casters 212, 312, 412, 512 and 612 and the like, and these elements maybe depicted in the figures but will not be discussed in any detail, asthe structure and operation of such elements can be substantiallysimilar between embodiments. Joystick 140, which is described in moredetail below, is depicted as being the same in each of the vehicleembodiments.

FIG. 2 depicts an all-electric vehicle 200 which is similar in manyrespects to vehicle 100, with the primary difference being the use ofbattery 224 to power the electric transaxles 230L, 230R, and mowerblades 219 without the need for a separate engine. Bus 234 connectscontrollers 232M and 232S and master controller 232M is connected tojoystick 140. A charge receptacle 226 for battery 224 is also depicted.

FIG. 3 depicts another exemplary vehicle 300 having a pair ofhydrostatic transaxles 329L, 329R driving rear wheels 316L, 316R. Primemover 320 drives the transaxles 329R and 329L by means of a standarddrive/pulley system 323.

Controller 332 is depicted as being centrally located under seat 315,but the location of this component and others, such as battery 324, canbe modified and are dependent on the vehicle size and other factors. Acontrol panel 350 provides the operator with control of certain vehiclefunctions and information about the status of vehicle 300. It will beunderstood that an operator interface, such as control panel 350, may beprovided in addition to joystick 140 for any of the vehicles describedherein, although this additional operator interface is not shown inorder to simplify the other vehicle figures.

Controller 332 receives power from battery 324 and is connected tojoystick 140 by conductor 341. Electric displacement actuators 331L,331R control the output of transaxles 329L, 329R, respectively, based oninput from controller 332, and are connected thereto by means ofconductors 336. Sensors 333L, 333R also provide controller 332 withinformation about the position of the swash plates (not shown) insidetransaxles 329L, 329R and are connected to controller 332 by means ofconductors 338. Speed sensors 335L, 335R are used to indicate the actualspeed of rear driven wheels 316L, 316R, and are connected to controller332 by means of conductors 337. Electric displacement actuators 331L,331R may be similar to those depicted in U.S. patent application Ser.No. 14/104,979, the terms of which are incorporated herein by reference.Transaxles 329R and 329L may be Hydro-Gear ZT-2800 integrated zero-turntransaxles, as depicted in U.S. Pat. No. 7,134,276, the terms of whichare incorporated herein by reference. Electric displacement actuators331L and 331R are shown as being integral to transaxles 329L, 329R butthey could also be separately connected thereto.

FIG. 4 represents another hybrid vehicle 400 using prime mover 420 topower a pair of separate hydraulic pumps 446L, 446R, each with its ownelectric actuator 447L, 447R (designated as “eA” in the drawing), todrive rear wheels 416L, 416R, respectively. Single controller 432 isconnected to battery 424, speed sensors 435L and 435R, electricactuators 447L and 447R, and joystick 140 in a manner similar to thatdescribed above. Standard hydraulic lines 453 are used to connect pump446L to motor 451L, pump 446R to motor 451R, and all of the foregoing toreservoir 454.

It will be understood that the depiction of the batteries 124, 224, 324,424, 524 and 624 in FIGS. 1-4, 5 and 6 is representational, and that ineach vehicle more than one battery may be used. For example, in FIG. 1,battery 124 could be four 12-volt batteries with each alternator 121charging a pair of the batteries.

The joystick controller assembly disclosed herein could also be used ina vehicle incorporating electric wheel hub motors. For example, FIG. 5represents a vehicle 500 incorporating a pair of wheel hub motors 539Land 539R on which the wheels 516L and 516R, respectively, are mounted.Vehicle 500 is similar in many respects to vehicle 100, with similarlynumbered elements being the same as or similar to those previouslydiscussed. As can be seen, certain elements such as controllers 532S and532M and prime mover 520 are disposed in a different location than inprior embodiments, demonstrating the flexibility of the design. Asbefore, joystick 140 is connected to master controller 532M, and the twocontrollers 532M and 532S are connected by bus 534 and are alsoconnected to the separate wheel hub motors 539R and 539L, respectively.Prime mover 520 powers a single alternator 521, which powers the battery524.

FIG. 6 represents another vehicle 600 incorporating wheel hub motors639L, 639R, which can be the same as those previously described. Thisembodiment is an all-electric vehicle similar in many respects to thatdepicted in FIG. 2 and, while similarly numbered elements are again thesame or substantially the same as those in other embodiments, thisfigure depicts additional flexibility of the design including, forexample, the mounting of multiple batteries 624 and the connection ofthese batteries 624 to the wheel hub motors 639L and 639R by way of acontroller 632 that also controls an electric mowing deck 617. A chargereceptacle 626 is also provided.

Joystick 140, which is depicted as being the same in each of the vehicleembodiments, is shown in more detail in FIG. 7, and can be similar inmany respects to a standard joystick. It comprises a base 149 to connectto the vehicle in a known manner. A vertical stalk or stick 143 pivotsabout a pivot point at its base in all directions akin to a standardjoystick, as shown by the X and Y axes in FIG. 7, creating a pluralityof pivot positions that can be communicated to the controller of avehicle, such as controller 332. As shown by arrows 156, stick 143 mayalso rotate about a vertical axis 144 (i.e., the Z axis), creating aplurality of rotational positions that can be communicated to thecontroller of a vehicle, such as controller 332. Pushbutton 145 may beused as a selector switch to provide additional functionality, asdescribed below.

FIGS. 8-19 are representational figures depicting various possibilitiesfor operating the vehicles depicted herein. FIGS. 8, 11, 14 and 17 aresimilar depictions of sixteen possible positions 1 through 16 ofjoystick 140; it will be understood that joystick 140 is infinitelyvariable, so these specific positions are merely representative ofselected positions for purposes of understanding the differentprogramming options available with this system. The following disclosurereferences vehicle 300 of FIG. 3 and the elements thereof merely forconvenience of description, as it would apply to the other vehiclesdisclosed herein and other embodiments.

FIGS. 8, 9 and 10 depict a first driving mode, and specifically one withno separate controls or limitations on the operation of the vehicle. InFIG. 8, the arrows next to the position numbers depict the relativespeeds of the left driven wheel 316L and right driven wheel 316R of zeroturn vehicle 300. Position 1 depicts both driven wheels 316L, 316Rmoving forward at full speed, so arrows 1 a and 1 b are of equal length.It will be understood that as the joystick moves from the zero-zeroposition out to each position 1 through 16 along the vectors shown inFIG. 8, the speeds of the left and right wheels will vary but willremain at a relative difference with respect to one another (or at norelative difference, e.g., at positions 1 and 9). This applies to theother driving modes depicted in later figures as well. In the graph ofFIG. 9, the horizontal axis represents the rotational speed anddirection of the left drive 329L output and associated left driven wheel316L, whereas the vertical axis represents the rotational speed anddirection of the right drive 329R output and associated right drivenwheel 316R. Thus, position 1 similarly shows right driven wheel 316Rrotating forward at full speed, while left driven wheel 316L is alsorotating forward at full speed, meaning that vehicle 300 is operating atits full forward speed.

Similarly, position 9 in FIG. 8 shows arrows 9 a and 9 b in fullreverse; this position represents joystick 140 being pulled all the wayback, such that both driven wheels 316L, 316R are at full speed in thereverse direction, moving the vehicle 300 backwards at full speed, asrepresented at position 9 in FIG. 9.

Position 2 shows both driven wheels moving forward, but with left drivenwheel 316L turning faster than right driven wheel 316R, resulting in arelatively gentle turn to the right, as seen in FIG. 10. Arrow 2 a isthus longer than arrow 2 b and represents a greater speed for leftdriven wheel 316L than for right driven wheel 316R. Position 3 showsleft driven wheel 316L moving at full speed forward, as shown by arrow 3a, while right driven wheel 316R is stopped, shown by the dot at 3 b inFIG. 8. This represents a sharp turn of vehicle 300 to the right, asdepicted by position 3 in FIG. 10.

As joystick 140 is pivoted, or canted, further to the right, it willreach position 4 where right driven wheel 316R is now moving in reverseat a reduced speed (arrow 4 b) and left driven wheel 316L is stillmoving forward at full speed (arrow 4 a), resulting in an even moredramatic right hand turn, as shown in FIG. 10. When joystick 140 ispivoted to position 5, the two driven wheels 316L and 316R are moving atthe same speed, but in opposite directions, resulting in a true zeroturn operation. This is represented by arrows 5 a and 5 b being the samelength.

It will be understood that operation in the different quadrants depictedin FIG. 9 will move the vehicle 300 in the same manner, but in differentdirections. That is, moving the joystick 140 from position 1 to 16 to 15to 14 to 13 will result in a left turn of vehicle 300 that becomesgradually sharper until vehicle 300 is performing a zero turn operationto the left.

Similarly, as the joystick 140 then continues to move in thecounter-clockwise direction from position 13 to position 9, the vehiclewill leave the left zero turn mode of position 13 and begin backing up,with the rear of the vehicle 300 moving to the right, as shown, e.g., bypositions 12, 11 and 10 in FIG. 10, until the vehicle is moving inreverse.

FIGS. 11, 12 and 13 are similar to those above, but depict a differentdriving mode, specifically one for vehicle 300 with a speed controlfunction added to the controller 332. The shorter arrows 5 a, 5 b and 13a, 13 b in FIG. 11 adjacent to positions 5 and 13 show that thecontroller 332 limits the speed of driven wheels 316L and 316R duringzero turn operations. This limitation can be particularly important forsafety and ease of operation, to prevent vehicle 300 from being throwninto a full speed zero turn operation at high speed.

Note also that in FIG. 11, the arrows 9 a and 9 b adjacent position 9are also shorter than the arrows 1 a and 1 b adjacent position 1,demonstrating a speed limit on full reverse speed. The shape 70 in FIG.12 depicts the range of speeds and motion permitted by the controllerwhile the profile or outer boundary of shape 70 represents the maximumoperating conditions allowed by the controller 332 programming. Axes 71and 72 represent the reduced range of speed at zero turn positions 5 and13, while axis 73 represents the reduced range of speed at full reverseposition 9, and axis 74 represents the full forward speed at position 1.The curves connecting these positions create the boundary of shape 70,where the vehicle 300 may operate at any point on or inside thisboundary defining shape 70.

The user could alternate between the programming scheme, or drivingmodes, of FIGS. 11, 14 and 17 by use of pushbutton 145. For example, thesystem could be programmed such that the scheme of FIG. 11 is thedefault, and activation of pushbutton 145 provides the twist tozero-turn capability of FIG. 14. Control panel 350 may be used torequire further operator input to prevent unintentional switchingbetween travel mode programs; e.g., an operator of vehicle 300 may berequired to press a button or activate a switch of control panel 350 inaddition to pressing pushbutton 145 in order to select a differenttravel mode. Further programming parameters may also require vehicle 300to be stopped or in a neutral drive state to select a different travelmode.

FIGS. 14, 15 and 16 are a set of drawings similar to the FIGS. 11, 12and 13, but representing a different set of programming for controller332 and thus a different driving mode. In this embodiment, joystick 140now includes a twist component, which permits the user to enter zeroturn by rotating or twisting the stick 143 about its vertical axis 144.Rotation in the clockwise direction, denoted by arrow/position 18,results in vehicle 300 making a zero turn in the clockwise direction.Similarly, rotation in the counter-clockwise direction, denoted byarrow/position 17, results in vehicle 300 making a zero turn in thecounter-clockwise direction. The degree of twist applied to stick 143 bythe vehicle operator determines the speed of the zero turn. Each of theplurality of driving modes maps a different set of speeds and directionsfor each of the driven wheels onto the plurality of rotational positions(e.g., the driving modes of FIGS. 14, 17, and 20), including somedriving modes where the rotational positions are disabled (e.g., thedriving modes of FIGS. 8 and 11). Controller 332 is also programmablesuch that movement of the joystick to the full left position 13 or thefull right position 5 results in the vehicle stopping, instead ofperforming the zero turn operation as in the prior embodiments, as shownat positions 5 and 13 in FIG. 14. The range of possible speed anddirection combinations of vehicle 300, as depicted by shapes 80 a and 80b in the graph of FIG. 15, is more limited than in the prior embodiment,and shape 80 a is smaller than shape 80 b due to the reduced reversespeed being programmed in this embodiment. Vehicle 300 may be operatedat any of the speed and direction combinations located on or inside theboundaries of the two shapes 80 a and 80 b of FIG. 15, plus anywherealong the diagonal axis connecting the two zero turn maximum speedpositions 17 and 18 which are located outside shapes 80 a and 80 b.

Each of the plurality of driving modes maps a different set of speedsand directions for each of the driven wheels onto the plurality of pivotpositions. A further advantage of the driving mode depicted in FIG. 14is that it may be considered more intuitive than the driving modes in,e.g., FIGS. 8 and 11. Specifically, in the modes shown in FIGS. 8 and11, when the joystick is pivoted or canted to a position to the back andright with respect to the user (e.g., positions 6, 7 or 8) the vehiclewill move in reverse, to the left (i.e., to the opposite side as theuser may expect). On the other hand, in the driving mode shown in FIG.14, when the joystick is pivoted to a position to the back and rightwith respect to the user (e.g., positions 6, 7 or 8) the vehicle willmove in reverse, to the right (i.e., in the direction that the user mayexpect). Similar differences are shown when the joystick is pivoted tothe back and the left with respect to the user (e.g., positions 10, 11and 12).

A potential drawback of the driving modes which incorporate stoppositions 5 and 13 is that a user driving vehicle 300 in a tight left orright turn, such as one mowing a tight circle around an object, couldinadvertently move the joystick to the stopped positions 5 or 13. Thismay cause aggravation and delay in completing the job. To address thisconcern, FIG. 20 represents another programming modification forcontroller 332, and a physical modification of joystick 140, wherebyelements S-1 and S-2 represent physical stops restricting the movementof joystick 140 to restrict or prevent it from moving into a stoppedposition from either the forward or reverse directions. This permitsvehicle 300 to have a minimum turning radius determined by the vehicleparameters, so that the user can fully pivot the joystick 140 in thedesired direction without concern that the vehicle will hit the stoppedposition. FIG. 20 is otherwise similar to FIG. 14, with the positions 1through 16 representing the same joystick positions and correspondingvehicle movement, while arrows/positions 17 and 18 represent thetwist-to-zero-turn mode of operation. This figure also depicts varioussectors A through G, with sector A representing full forward speed beingallowed while traveling straight or in a wide turn. The two sectors Brepresent positions where forward speed is reduced as the vehicle 300turns left or right in a tighter turn. This reduction is preferablyprogrammed as a gradual speed reduction as the vehicle moves into aprogressively tighter turn. Sectors C represent positions where themaximum reduction is applied to forward speeds while in very tightturns, prior to hitting either of the stops S-1. Similarly, sector Grepresents full reverse speed being allowed while traveling straight orin a wide turn. Sectors F represent positions where reverse speed isreduced as the vehicle 300 turns left or right in a tighter turn. Thisreduction is also preferably programmed as a gradual speed reduction asthe vehicle moves into a progressively tighter turn. Sector E representspositions where the maximum reduction is applied to reverse speeds whilein very tight turns, prior to hitting either of the stops S-2. Sectors Drepresent a programmed stop function if the joystick 140 reachespositions 5 or 13. This is provided as a fail-safe feature in the eventeither of the stops S-1 or S-2 are defeated or fail for any reason. Thephysical stop sectors S are bounded by stops S1, S2 and overlap theprogrammed stop sectors D. The joystick may ride along the stops S1 andS2 to aid the vehicle operator in controlling a tight turn within anallowed speed range. The size of the various sectors shown in FIG. 20 isexemplary and may be determined by the programmer to provide appropriateresponses of a particular vehicle.

FIGS. 17, 18 and 19 are another set of figures similar to the priorviews of FIGS. 11-16, and depict a system where the programming ofcontroller 332 is a combination of the prior two embodiments. That is,zero turn to the right may be accomplished by pivoting the joystick toposition 5 or by twisting it in the clockwise direction as denoted byposition 18, and zero turn to the left may be accomplished by pivotingthe joystick 140 to position 13 or by rotating it in a counterclockwisedirection as denoted by position 17. The allowed zero turn speed rangemay be programmed to be different depending on whether the zero turntravel mode is initiated by pivoting or twisting of joystick 140.Programming may also ensure that one of the two zero turn travel modescan only be entered by twisting of joystick 140 when it is in theneutral position. Shape 70 in FIG. 18 again represents the permissiblerange of vehicle speeds and directions. As noted above, for allembodiments, the references to controller 332 and vehicle 300 areexemplary only, as this invention can be used with the other vehiclesdepicted and other utility vehicles where this type of zero turnoperation and control is desirable.

The “twist” feature of joystick 140 could also be used in differentmanners, in addition to the twist-to-zero-turn embodiments previouslydescribed, and various modifications may be programmed into thecontroller. For example, the twist capability depicted in FIG. 14 aspositions 17 and 18 corresponding to zero turn for the vehicle could belimited to situations where stick 143 is in the zero-zero position onthe X-Y axes of FIG. 7, and the controller could be programmed such thatrotation of stick 143 about its Z axis could have different effects, orno effect at all, when stick 143 is not in this zero-zero position. Byway of example, for safety reasons one may wish to program thecontroller such that a twisting of stick 143 about its Z axis would haveno effect if the joystick is in one of the positions 1 through 16.Alternatively, the controller could be programmed to permit differentresponses if the joystick 140 is in one of these positions. For example,if joystick 140 is in position 1, which corresponds to the full aheadposition and both wheels are being rotated at the same speed, a twist inone direction would subtract rotational speed from one of the two driveunits to permit steering. This would be similar to moving the joystickto, for example, positions 2 or 16, but the twist feature may afford theuser a more refined steering sense and control over the vehicledirection.

The pushbutton feature of joystick 140 could also be used in differentmanners. For example, the programming of the controller, such ascontroller 632 shown in FIG. 6, could allow pushbutton 145 to activatean auxiliary function or device of vehicle 600, such as mowing deck 617,for example. Alternatively, the programming of controller 632 couldconditionally allow activation of an auxiliary function or device, suchas mowing deck 617, dependent upon the position of joystick 140 and/ormay disable an auxiliary function or device, such as mowing deck 617,dependent upon the position of joystick 140. Furthermore, throughprogramming of controller 632, a combination of vehicle 600 conditions,including the position of joystick 140, could be used to allowactivation or to disable an auxiliary function or device. It should alsobe noted that the pushbutton feature may comprise different switchtypes, such as locking or momentary, depending on the controlledfunction.

While specific embodiments of the invention have been described indetail, it will be appreciated by those skilled in the art that variousmodifications and alternatives to those details could be developed inlight of the overall teachings of the disclosure. Accordingly, theparticular arrangements disclosed are meant to be illustrative only andnot limiting as to the scope of the invention which is to be given thefull breadth of the appended claims and any equivalent thereof.

What is claimed is:
 1. A control system for use in a vehicle having apair of drive units, each drive unit independently powering a leftdriven wheel of the vehicle or a right driven wheel of the vehicle,wherein the vehicle is capable of moving in a plurality of forwarddirections, a plurality of reverse directions, a clockwise zero turnmotion, and a counterclockwise zero turn motion, the control systemcomprising: a power source; a controller powered by the power source andin electrical communication with the pair of drive units, the controllerhaving programmed therein a plurality of driving modes selectable by auser, the plurality of driving modes comprising at least a first drivingmode and a second driving mode; and a joystick electronically connectedto the controller to provide user inputs to the controller to separatelycontrol the rotational speed and direction of the left and right drivenwheels of the vehicle, the joystick being pivotable about a pivot pointbetween a plurality of pivot positions, each of the plurality of pivotpositions corresponding to a particular rotational speed and directionof each of the driven wheels; wherein each of the plurality of drivingmodes maps a different set of rotational speeds and rotationaldirections for each of the driven wheels onto the plurality of pivotpositions and each of the plurality of driving modes has a maximumclockwise zero turn speed, a maximum counterclockwise zero turn speed, amaximum full forward speed and a maximum full reverse speed; andwherein, in the first driving mode, the rotational speed of the drivenwheels at the maximum full forward speed is equal to the rotationalspeed of the driven wheels at the maximum full reverse speed, and in thesecond driving mode, the rotational speed of the driven wheels at themaximum full forward speed is greater than the rotational speed of thedriven wheels at the maximum full reverse speed; and wherein, in atleast one of the plurality of driving modes, the rotational speed of thedriven wheels at both the maximum clockwise zero turn speed and themaximum counterclockwise zero turn speed are both less than therotational speed of the driven wheels at either the maximum full forwardspeed or the maximum full reverse speed.
 2. The control system of claim1, further comprising a selector switch for selecting one of theplurality of driving modes.
 3. The control system of claim 1, whereinthe joystick is rotatable in both a clockwise direction and acounterclockwise direction about a vertical axis to create a pluralityof rotational positions, wherein rotation of the joystick in theclockwise direction moves the vehicle in the clockwise zero turn motion,and rotation of the joystick in the counterclockwise direction moves thevehicle in the counterclockwise zero turn motion.
 4. The control systemof claim 3, further comprising a pushbutton located on the joystick andacting as a selector switch for selecting one of the plurality ofdriving modes.
 5. The control system of claim 3, wherein at least one ofthe plurality of driving modes permits the controller to process pivotposition information and rotational position information of the joystickin combination, to control the rotational speed and direction of each ofthe driven wheels.
 6. The control system of claim 5, wherein at leastone of the plurality of driving modes permits the vehicle to be steeredin the plurality of forward directions by varying the rotationalposition of the joystick when the joystick is pivoted forward from thevertical axis.
 7. The control system of claim 1, wherein in one of theplurality of driving modes, when the joystick is moved to one of theplurality of pivot positions, to the back and right with respect to avertical axis of the joystick, the vehicle will move in reverse to theleft, and when the joystick is moved to a second of the plurality ofpivot positions, to the back and left with respect to the vertical axis,the vehicle will move in reverse to the right.
 8. The control system ofclaim 7, wherein in another of the plurality of driving modes, when thejoystick is moved to a third of the plurality of pivot positions, to theback and right with respect to the vertical axis, the vehicle will movein reverse to the right and when the joystick is moved to a fourth ofthe plurality of pivot positions, to the back and left with respect tothe vertical axis, the vehicle will move in reverse to the left.
 9. Thecontrol system of claim 8, wherein the plurality of driving modesfurther comprises a third driving mode wherein rotation of the joystickabout the vertical axis to a first rotated position moves the vehicle inthe clockwise zero turn motion and rotation of the joystick about thevertical axis to a second rotated position moves the vehicle in thecounterclockwise zero turn motion.
 10. The control system of claim 9,wherein the joystick must be in a vertical orientation to enable thethird driving mode.
 11. The control system of claim 10, furthercomprising a fourth drive mode wherein at least two of the plurality ofpivot positions comprise programmed stop positions where the left andright driven wheels are not powered.
 12. The control system of claim 1,wherein the joystick further comprises a physical stop to prevent thejoystick from accessing a predetermined subset of the plurality of pivotpositions.
 13. The control system of claim 12, wherein the predeterminedsubset of the plurality of pivot positions corresponds to zero rotationof the driven wheels.
 14. The control system of claim 1, wherein thecontroller comprises a first controller operatively connected to a firstof the pair of drive units, and a second controller operativelyconnected to a second of the pair of drive units and the firstcontroller is operatively connected to the second controller.
 15. Acontrol system for use in a vehicle having a pair of drive units, eachdrive unit independently powering a left driven wheel of the vehicle ora right driven wheel of the vehicle, wherein the vehicle is capable ofmoving in a plurality of forward directions, a plurality of reversedirections, a clockwise zero turn motion, and a counterclockwise zeroturn motion, the control system comprising: an electric controllerpowered by a power source and in communication with the pair of driveunits; and a joystick electronically connected to the electriccontroller to provide user inputs to the electric controller to controlthe rotational speed and direction of the two separate driven wheels ofthe vehicle, the joystick comprising: a vertical stalk pivotable about apivot point between a plurality of pivot positions, each of theplurality of pivot positions corresponding to a particular rotationalspeed and direction of the left driven wheel and the right driven wheel,and twistable about a vertical axis extending through the pivot pointbetween a plurality of twist positions; and a selector switch forselecting one of a plurality of driving modes stored in the electriccontroller; wherein each of the plurality of driving modes maps adifferent set of speeds and directions for each of the driven wheelsonto the plurality of pivot positions and the plurality of twistpositions, and each of the plurality of driving modes has a maximumclockwise zero turn speed, a maximum counterclockwise zero turn speed, amaximum full forward speed, and a maximum full reverse speed; wherein atleast one of the plurality of driving modes comprises a zero turn modewhere the vertical stalk of the joystick may be twisted in a clockwisedirection about the vertical axis to move the vehicle in the clockwisezero turn motion and in a counterclockwise direction about the verticalaxis to to move the vehicle in the counterclockwise zero turn motion;and wherein, in at least one of the plurality of driving modes, therotational speed of the driven wheels in both the maximum clockwise zeroturn speed and the maximum counterclockwise zero turn speed are bothless than the rotational speed of the driven wheels at the maximum fullforward speed.
 16. The control system of claim 15, wherein, in at leastone of the plurality of driving modes, the maximum full reverse speed isless than the maximum full forward speed.
 17. The control system ofclaim 16, wherein, in at least one of the plurality of driving modes,the rotational speed of the driven wheels in both the maximum clockwisezero turn speed and the maximum counterclockwise zero turn speed is lessthan the rotational speed of the driven wheels at the maximum fullreverse speed.
 18. A control system for use in a vehicle having a leftdrive unit independently powering a left driven wheel of the vehicle anda right drive unit independently powering a right driven wheel of thevehicle, wherein the vehicle is capable of moving in a plurality offorward directions, a plurality of reverse directions, a clockwise zeroturn motion, and a counterclockwise zero turn motion, the control systemcomprising: a power source; a controller powered by the power source andin electrical communication with the left drive unit and the right driveunit, the controller having programmed therein a plurality of drivingmodes selectable by a user, the plurality of driving modes comprising atleast a first driving mode and a second driving mode; and a joystickelectronically connected to the controller to provide user inputs to thecontroller to control the rotational speed and direction of the leftdriven wheel and the right driven wheel, the joystick being pivotablebetween a plurality of pivot positions, the plurality of pivot positionscomprising: a first set of pivot positions where the controller causesthe right driven wheel to be rotated in a forward direction at at leasta first rotational speed and the left driven wheel to be either (i)rotated forward at a rotational speed less than the rotational speed ofthe right driven wheel, (ii) stopped, or (iii) rotated in reverse,depending on a specific selected pivot position within the first set ofpivot positions and whereby the vehicle will turn in a forward leftdirection at different turning radii for each specific pivot positionwithin the first set of pivot positions, and as the turning radius ofthe vehicle decreases, the controller causes the right drive unit toreduce the forward rotational speed of the right driven wheel; and asecond set of pivot positions where the controller causes the leftdriven wheel to be rotated in a forward direction at at least the firstrotational speed and the right driven wheel to be either (i) rotatedforward at a rotational speed less than the first rotational speed ofthe left driven wheel, (ii) stopped, or (iii) rotated in reverse,depending on a specific selected pivot position within the second set ofpivot positions and whereby the vehicle will turn in a forward rightdirection at different turning radii for each specific pivot positionwithin the second set of pivot positions and as the turning radius ofthe vehicle decreases, the controller causes the left drive unit toreduce the forward rotational speed of the left driven wheel; whereineach of the plurality of driving modes maps a different set ofrotational speeds and rotational directions for each of the drivenwheels onto the plurality of pivot positions and each of the pluralityof driving modes has a full forward position and a full reverseposition.
 19. The control system of claim 18, wherein, in the firstdriving mode, the rotational speed of the driven wheels in the fullforward position is equal to the rotational speed of the driven wheelsin the full reverse position, and in the second driving mode, therotational speed of the driven wheels in the full forward position isgreater than the rotational speed of the driven wheels in the fullreverse position.
 20. The control system of claim 18, wherein theplurality of pivot positions further comprises: a third set of pivotpositions where the controller causes the right driven wheel to berotated in a reverse direction at a third rotational speed and the leftdriven wheel to be either (i) rotated in reverse at a fourth speed lessthan the third rotational speed, (ii) stopped, or (iii) rotated forward,depending on a specific selected pivot position within the third set ofpivot positions and whereby the vehicle will turn in a reverse leftdirection at different turning radii for each specific pivot positionwithin the third set of pivot positions; and a fourth set of pivotpositions where the controller causes the left driven wheel to berotated in a reverse direction at the third rotational speed and theright driven wheel to be either (i) rotated in reverse at a speed lessthan the third rotational speed, (ii) stopped, or (iii) rotated forward,depending on a specific selected pivot position within the fourth set ofpivot positions and whereby the vehicle will turn in a reverse rightdirection at different turning radii for each specific pivot positionwithin the fourth set of pivot positions.
 21. The control system ofclaim 20, wherein within the third set of pivot positions, as theturning radius of the vehicle decreases, the controller causes the rightdrive unit to reduce the rotational speed of the right driven wheel and,within the fourth set of pivot positions, as the turning radius of thevehicle decreases, the controller causes the left drive unit to reducethe rotational speed of the left driven wheel.
 22. The control system ofclaim 18, wherein the joystick may be twisted in a clockwise directionabout a vertical axis to move the vehicle in the clockwise zero turnmotion and in a counterclockwise direction about the vertical axis tomove the vehicle in the counterclockwise zero turn motion.